The present invention relates to a method for controlling a drive unit equipped with an internal combustion engine, with which the change of an output variable of the drive unit for a load change is limited and in which a desired course for the output variable of the drive unit for the load change is formed and the desired course of the output variable is converted by changing the air input to the internal combustion engine. The present invention also relates to an apparatus for controlling a drive unit with an internal combustion engine, which includes a limiting device for limiting a change of an output variable of the drive unit for a load change, a formulating device for forming a desired course for the output variable for the load change and a conversion device for changing the desired course for the output variable by changing the air intake of the internal combustion engine.
In order to avoid impacts in the drive train of a vehicle powered by an internal combustion engine during load change, i.e. during the zero passage of the coupling torque, the change of the coupling torque must be limited. The air intake system of the Otto engine has inertia during uniform operation, which can be described to good approximately as PT1 behavior. A preliminary value is derived from an adjustment curve for adjusting an actual value of the coupling torque by means of an air intake of the internal combustion engine according to an actual value of the coupling torque, the motor speed and the drive train gear ratio. The limitation during a positive load change, i.e. a transition from thrust or pushing operation to pulling operation, is accomplished by an ignition angle engagement. This preliminary value is applied with the help of characteristic curves depending on the actual value of the coupling torque, the motor speed and the drive train gear ratio. In this way a rapid build up of the actual value of the coupling torque is possible after zero passage of the coupling torque.
During a negative load change during shifting from pulling operation to thrust or pushing operation a changed target value for the coupling torque is filtered by both the adjusting curve for air intake of the internal combustion engine and a so-called crank shaft adjusting curve under the influence of ignition angle and/or fuel injected into the internal combustion engine by means of PT1 component. An ignition angle engagement is triggered in order to speed up the decrease in the actual value of the coupling torque.